Residential and commercial buildings represent a prime opportunity to improve energy efficiency and sustainability in the United States. The buildings sector alone accounts for 40% of the United States' yearly energy consumption (40 quadrillion BTUs, or “quads”, out of 100 total), and 8% of the world's energy use. Lighting and thermal management each represent about 30% of the energy used within a typical building, which corresponds to around twelve quads each of yearly energy consumption in the US. Windows cover an estimated area of about 2,500 square km in the US and are a critical component of building energy efficiency as they strongly affect the amount of natural light and solar gain that enters a building. Recent progress has been made toward improving window energy efficiency through the use of inexpensive static coatings that either retain heat in cold climates (low emissive films) or reject solar heat gain in warm climates (near-infrared rejection films).
Currently, static window coatings can be manufactured at relatively low cost. However, these window coatings are static and not well suited for locations with varying climates. A window including an electrochromic (EC) device overcomes these limitations by enhancing window performance in all climates.
However, one of the shortcomings of conventional EC windows is the inability to achieve a sufficiently dark state to allow for use in privacy applications. Accordingly, there is a need for smart windows suitable for privacy applications.